Treatment of hydrocarbon gases



Patented Feb. 13, 1940 v UNITED STATES PATENT OFFlC 2.189.815 TREATMENT OF nrnnocannom Gases Jacque 0. Morrell and AristidY. Grosse, Chicago,-

Ill., assignors to Universal OiLProducta Company, Chicago, 111., a corporation or Delaware No Drawing. Application February 27,1936, serial No. 66.0%

9 Claims.

though hydrocarbons up to and including octane and higher homologs may be treated.

In a more specific sense, the invention is concerned with a process vfor converting the low boiling members of the paraiiin series of hydrocarbons into their corresponding olefins which contain two atoms of hydrogen less per molecule and consequently have one double bond between carbon atoms. v

There is a large commercial production of gaseous paraflln hydrocarbons. They occur in very large quantities in natural gas, particularly those gases associated with the production of crude oil and commonly known as casinghead gases, and this supply is further augmented by the gases produced in cracking oils for the production of go gasoline, although this latter type of pyrolytically produced gas contains substantial quantities of oleflns as well as paramnic hydrocarbons.

The greater part of the paraflln gas production is used merely for domestic and industrial fuel 5 purposes and not as a source of hydrocarbon derivatives, on account of the unreactive character of its components in comparison with their olefinic counterparts. A large part of the production is wasted to the atmosphere.

30 In one specific embodiment the invention comprises the dehydrogenation of gaseous paramn hydrocarbons, particularly those containing three and four carbon atoms, such as propane and the butanes, at elevated temperatures in the 5 presence of catalysts comprising essentially magnesium oxide supporting minor amounts of lower oxides oi. vanadium. Lowerboiling liquid hydrocarbons may also be treated according to the process although it is to. be distinctly understood 40 that such treatment is not the full equivalent of the treatment of gaseous hydrocarbons.

In the present instance, the catalysts which are preferred for selectively dehydrogenating the lower boiling parai'iinic hydrocarbons have been 45 evolved as the result of a large amount of investigation with catalysts having a dehydrogenating action upon various types of hydrocarbons such as are encountered in the fractions produced in the distillation and/or pyrolysis oi pe- 5o troleum and other naturally occurring hydrocarbon oil mixtures. The criterion ol'an acceptable dehydrogenatlng catalyst is that it shall split ofl' hydrogen without inducing excess scission oi the bonds'between carbon atoms orcarbon separa- 55 tion'. Inthe present invention catalyst mixtures comprising essentially major amounts of magnesium oxide and minor amounts of lower oxides of vanadium, such as for example V203 or V204,

' andin some cases some V0, are used. Mag

nesium oxide alone functions to a very limited 5 extent as a dehydrogenating catalyst in the above sense, and the tendency to selective splitting ofi of hydrogen on the one hand has been found to be greatly increased and the tendencyto scission oi the carbon-to-carbon bond on the other hand 10 has been found to be greatly lessened by the use of the vanadium oxides mentioned, so that the dehydrogenating action is rendered much more definite and effective, the yield of oleflnic hydrocarbons is much greater, and the life of the catal8 lyst composite is extended.

Our investigations have also demonstrated that the catalytic eiiiciency of magnesium oxide is greatly improved by the presence of oxides of vanadium even-in minor amounts, usually of the order of less than 10% by weight of the magnesia. It is most common practice to utilize catalysts comprising 2 to 5% by weight of these vanadium oxides.

The mineral magnesite from which magnesium oxide is conveniently prepared to furnish base material for the present type of catalyst is most commonly encountered in a massive or earthy variety and rarely-in crystal form, the crystals being usually rhombohedral. In many natural magnesites, the magnesium oxide may be replaced to the extent of several percent by ferrous oxide. The mineral is of quite common occurrence and readily obtainable in quantity at a reasonable figure. "The pure compound begins to decompose to form the oxide at a. temperature of 350 C. (663 F.). though the rate of decomposition only reaches a practical value at considerably higher temperatures, usually of the order of 800 C. (14'l2 F.) tof900 C. (1652 F.). This mineral is related to dolomite, the mixed carbonate of calcium and magnesium, this latter mineral, however, not being of as good service as the relatively pure magnesite in the present instance. Magnesium carbonate prepared by precipitation or other chemical methods may be used alternatively in place of the natural mineral, thus permitting its use as the active constitueTit of masses containing spacing materials of relatively inert character and, in some cases,

allowing the production of catalysts of higher efliciency and longer life.

In making up catalyst composites of the character and composition which according to the present invention have been found specially well suited for catalyzing dehydrogenation reactions, the following is the simplest and generally the preferred procedure. Natural magnesite or the precipitated carbonate is calcined at temperatures from 800 C. (1472 F.) to 900 C. (1652 F.) to produce material containing a relatively high percentage of magnesium oxide (usually over and the calcined material is ground and sized or pelleted to produce granules or pellets, respectively, of approximately 4-30 mesh. The sized particles are then caused to absorb compounds which will ultimately yield oxides of vanadium on heating to a proper temperature by stirring them with warm and aqueous solutions of soluble vanadium compounds, such as for example .ammonium metavanadate having the formula NH4VO3 which is sufiiciently soluble in warm water to render it readily utilizable. Vanadyl nitrate may also be employed, a solution of this salt being prepared by adding either silver or barium nitrate to solutions of vanadyl chloride or vanadyl sulfates. The carbonate of vanadium is rather rare and ordinarily will not be employed as a source of the oxides. As a further alternative for making up the present types of catalysts, either vanadium pentoxide or the lower oxides may be mixed mechanically with the magnesia or if desired first made into a paste to insure thorough contacting and mixing and the paste then dried, ground and sized.

The mineral oxide of magnesium may sometimes be employed as base material (this oxide being known as periclase) whenever the same is readily available and its physical properties as well as its content of impurities permits. The mineral oxide occurs in granular form or in definite cubic or octahedral crystals and may contain in many cases besides relatively inert siliceous gangue materials small amounts of iron and manganese replacing a portion of the magnesium.

The magnesium oxide resulting from calcination at the temperatures mentioned has a high absorptive capacity for solutions and takes up rather large quantities of aqueous solutions without leaving any excess. Some of the salts of vanadium which are utilizable as a source of the primary pentoxide are, however, not extremely soluble in water and in order to get a sufiicient quantity of the desired oxides deposited upon the magnesium oxide it may be necessary at times to add the aqueous solutions in successive portions with intermediate drying stages rather than to add the magnesium oxide to a dilute aqueous solution and depend upon the absorptive capacity for the extraction of the salt.

The oxides resulting from the decomposition of many of the soluble vanadium compounds are principally those in which vanadium exhibits the higher valences,'such as in vanadium pentoxide V205. These oxides, however, are preferably reduced by hydrogen, or by the paraflinic gases and the other gases resulting from their decom position in the first stages of the dehydrogenation reactions so that in any case the essential catalysts for the larger portion of the period of service appear to be the lower oxides.

One of the readily available and utilizable compounds for adding vanadium oxides to magnesium oxide is the ammonium vanadate mentioned in the preceding paragraph. This compound is sufficiently soluble in warm water to render it utilizable, andafter adding the amount corresponding to the amount of vanadium found most suitable the granules are dried, first at C. for about two hours and then at temperatures of the order of 200-250 C. for some hours longer. If desired the vanadium pentoxide present on the magnesium oxide may then be reduced by hydrogen previous to the use of the composite catalyst in dehydrogenation reactions. A very serviceable catalyst is made by dissolving approximately 15.4 parts by weight of the ammonium metavanadate in 200 parts by weight of hot water, and adding the solution in two approximately equal successive portions to 250 parts by weight of magnesium oxide of 10-12 mesh particle size. The best procedure is usually to dry the magnesia particles at 100 C. after the addition of the first half of the vanadate solution and then add the other half of the solution to the air dried material followed by further drying. The percentage of vanadium on the magnesia particles is then about 2.75. It should be emphasized that the oxides of vanadium are the essential catalysts in the composite since without them the magnesia possesses limited dehydrogenating ability.

In practicing the dehydrogenation of paraffinic gases according to the present process, a solid composite catalyst prepared according to the foreging briefly outlined methods is used as a filler in a reaction tube or chamber in the form of particles of graded size or small pellets, and the gas to be dehydrogenated is passed through the catalyst after being heated to the proper temperature, usually within the range of from about 400 to 770 C. (752 to 1400" F.). The most commonly used temperatures, however, are around 500 C. to 600 0. (932 to 1112" F.) The catalyst tube is heated exteriorly to maintain the proper reaction temperature. The pressure employed may be sub-atmospheric, atmospheric or slightly superatmospheric of the order of from 50 to 100 pounds per square inch. While pressures up to 500 pounds per square inch may be employed in some cases, pressures of the order of atmospheric or below are generally preferred. The time during which the gases are exposed to dehydrogenating conditions in the presence of the preferred catalysts is comparatively short, usually below twenty seconds.

The exit gases from the catalytic tube or chamber may be passed through selective adsorbents to combine with or absorb the olefin or olefin mixture produced, or the olefins maybe selectively polymerized by suitable catalysts, caused to alkylate other hydrocarbons such as aromatics or paraflins or treated directly with chemical reagents to produce desirable and commercially valuable derivatives. After the olefins have been removed the residual gases may be recycled for further dehydrogenating treatment with or without removal of hydrogen.

The present types of catalysts are selective in removing two hydrogen atoms from a paraflin molecule to produce the corresponding olefin without furthering to any great degree undesirable side reactions, and because of this show an unusually high conversion of paraffins into olefins as will be shown in later examples. When the activity of these catalysts begins to diminish it is readily regenerated by the simple expedient of oxidizing with air or other oxidizing gas at a moderately elevated temperature, usually within the range employed in the dehydrogenating reactions. This oxidation effectlvely removes traces of carbon deposits which contaminate the surface of the particles and decrease their efficiency. It is characteristic of the present types of catalysts that they may be repeatedly regenerated without substantial loss of catalytic efliciency.

During oxidation with air or other oxidizing gas mixture in regenerating partly spent material there is evidence to indicate that the vanadium oxides such as V203 and V204 are to a large extent, if not completely, oxidized to V205, which may combine with the magnesium oxide to form a certain amount of various magnesium vanadates. The existence of several magnesium vanadates is known, but analyses have indicated that their composition is rather indefinite so that they may possibly be solid solutions rather than definite chemical compounds. These magnesium vanadates are later decomposed by contact with reducing gases in the first stages of service to reform the lower oxides of vanadium and regenerate the real catalyst and hence the catalytic activity.

Numerous experimental data could be adduced to indicate the results obtainable by employing the present type of catalyst to dehydrogenate paraflins, but the following example is suiliciently characteristic. I

A catalyst was prepared'by dissolving 15.4 parts by weight of ammonium meta in 200 parts by weight of hot water and adding the solution in two equal successive portions to 250 parts by weight of a 10 to 12 mesh calcined ma esite. After the addition of the first half of the solution the particles were somewhat damp and were dried at a steam temperature to remove excessive water. After this heating the second half of the solution was added and the dehydration repeated. During the heating period ammonia and water were evolved leaving vanadium pentoxide deposited on the magnesium oxide particles.

The final steps in the preparation of the catalyst comprised heating at 200-250 C. for several hours adding the particles to a catalyst chamber in which they were brought upto the necessaryreaction temperature for dehydrogenating the parafiinic gas mixture in a current of air and then subjected to the action of hydrogen at the operating temperature to produce the lower oxides, this change being accompanied by change in color from yellow to bluish gray.

Pure n-butane may be passed through the catalyst bed at a temperature of 500 C. and atmospheric pressure and the table summarizes the results which may be obtained:

' could'be readily regenerated Analyses of exit gases After a considerable period became fou1ed-with carbonaceousto its original eiii-' a stream of air at 500 C.

ciency by heating in present invention and its The character of the practical applications are sufiiciently developed 7 and exemplified by the foregoing specification and limited examples. However, neither section is to be construed as unduly limiting wide and proper scope. V We claim as our invention: 1. A process for the treatment of parafiinic hydrocarbons to produce the up s . uate t0 dehydrosenate 'hydrocarbonsto oftimethecatalyst deposit; but' (mate to dehydrogenate and convert said paraf-- finic hydrocarbons into olefin hydrocarbons, and recovering the olefin hydrocarbons thus formed.

2. A process for the treatment of normally gaseous parafilnic hydrocarbons, which comparafiinic hydrocarbons with a catalyst, comprising essentially a major pmportion of activated magnesite and a minor proportion of an oxide'of vanadium, at a. temperature adequate to dehydrogenate and convert said parafiinic hydrocarbons into olefin hydrocarbons. and recovering formed.

3. A process for'the treatment of paraifinic hydrocarbons to produce the corresponding olefinie hydrocarbons, which comprises subjecting paraflinic hydrocarbons to the action of a cata- 17st, comprising essentially a major proportion of magnesium oxide and a minor proportion of a lower oxide of vanadium, at a temperature adeand convert, said paraffinic hydrocarbons olefin hydrocarbons, and recovering the olefin 4- A process for the treatment of parafilnic hydrocarbons to produce hydrocarbons, which comprises subjecting paraffinic hydrocarbons to the action of a catalyst, comprising essentially a major proportion of magnesium oxide and a minor proportion of a compound of vanadium, at a temperature of from 400 to 800 C. todehydrogenate and convert said parafiinic hydrocarbons into olefin hydrocarbons, and recovering the olefin hydrocarbons thus formed.

5. A process for the treatment of parafiinic produce the corresponding 01efinic hydrocarbons, which comprises subjecting paraflinic hydrocarbons to the action of a catalyst, comprising essentially a major proportion of magnesium oxide and a minor proportion of a compound of vanadium. at a temperature of from 500 to 600 C. to' dehydrogenate and convert said paraflinic hydrocarbons into olefin bons, and recovering the olefin hydrocarbons thus formed.

into

the olefin hydrocarbons thus the corresponding olefinic hydrocarbons thus formed.

- '6. A process for the treatment of normally gaseous parafilnic hydrocarbons to produce the corresponding olefinic hydrocarbons, which comprises treating said paraflinic hydrocarbons with a catalyst, comprising essentially a major proportion of magnesium oxide and minor amounts of lower oxides of vanadium, at a temperature of from 400' to 800 C. to d hydrogenate and convert the parafiin hydrocarbons into olefin hydrocarbons, and recovering the latter.

V I. A proces for the treatment of normally gaseous paraiiinic hydrocarbons to produce the corresponding olefinic hydrocarbons, which comprises treating said normally: gaseous parafiinic hydrocarbons with a catalyst, comprising essentially magnesium oxide containing approximately two to five percent of-. an oxide of vanadium, ata temperature of fromr500 to 600 C. to dehydrogenate and convert the paraifin hydrocarbons into olefin hydrocarbons, latter 8. A process for the treatment of normally.

gaseous pamfllnic hydrocarbons to produce the corresponding hydrocarbons, which coinprim treating said gaseousparaiiinic hydrocarbons with a catalyst, comprising essentiaily magnesium oxide containing approximately two to five percent of an oxide of vanadium, at a. temperature of from 500 to 600 0., and for a. time period greater than 0.2 second and less than 10 seconds, to dehydrogenate and convert the paramn hydrocarbons into olefin hydrocarbons, and recovering the latter.

9. A process for treating paraflinic hydrocarbons which comprises subjecting the same under dehydrogenating conditions to the action of a mixture of a. major proportion 01' magnesium oxide and a minor proportion of a vanadium oxide. 5

JACQUE C. MORRELL. ARIB'I'ID V. GROSSE. 

